WO2009018224A1

WO2009018224A1 - Apparatus and method for making a new physical master

Info

Publication number: WO2009018224A1
Application number: PCT/US2008/071376
Authority: WO
Inventors: Douglas M. Carson
Original assignee: Doug Carson & Associates, Inc.
Priority date: 2007-07-27
Filing date: 2008-07-28
Publication date: 2009-02-05

Abstract

Method and apparatus for forming a new physical master (212) from which a population of replicated media (160) can be subsequently formed. A transduced pattern sequence (232) is sampled (304) by a sampling circuit (226) at a selected sampling frequency to provide a sequence of digitized samples (234). The sequence of digitized samples is selectively adjusted (306) by an adjustment circuit (240) to provide a sequence of adjusted digitized samples with signal transitions corresponding to preselected symbol lengths (250). The sequence of adjusted digitized samples is thereafter written (310) to a medium (178) to form a new physical master from which a population of replicated media can be formed. Preferably, a second sampling circuit (228) concurrently samples a second transduced pattern sequence (236) to provide a second sequence of digitized samples (238). The adjustment circuit concurrently adjusts and outputs the second sequence during the writing of the new physical master.

Description

APPARATUS AND METHOD FOR MAKING A NEW PHYSICAL MASTER

Background

Some types of data storage media are in the form of discs, which are rotated at a specified rate adjacent a data transducer. Data are often written to an optical disc as a pattern sequence of pits and lands (marks) that provide different optically reflective responses to an optical pickup mechanism.

Such media can be pre-recorded, or recordable. Pre-recorded media are often produced in a mastering process whereby a writing system, such as a laser beam recorder (LBR), selectively modulates a laser to selectively expose a master (such as a glass master with a layer of light sensitive material thereon). The exposed material is processed to provide a series of stampers, and the stampers are used to generate replicated discs such as in an injection molding or similar process.

While operable, establishing new production runs of replicated media can be difficult if additional replicas are desired at a later time. One approach is to use the original stampers used in a previous production run to generate additional replicas in a new production run. If not available, a new master can be created by reading off a replicated disc to generate a new light modulation sequence for the new master. While operable, these and other prior art approaches can provide replicas in the subsequent production run that have degraded characteristics as compared to those of the original production run.

Summary

Various embodiments of the present invention are generally directed to an apparatus and method for making a new physical master, such as for use in the production of a population of replicated optical discs. In accordance with various embodiments, a transduced pattern sequence is sampled by a sampling circuit at a selected sampling frequency to provide a sequence of digitized samples. The sequence of digitized samples is selectively adjusted by an adjustment circuit to provide a sequence of adjusted digitized samples with signal transitions corresponding to preselected symbol lengths. The sequence of adjusted digitized samples is thereafter written to a medium to form a new physical master from which a population of replicated media can be formed.

Preferably, a second sampling circuit concurrently samples a second transduced pattern sequence to provide a second sequence of digitized samples. The adjustment circuit concurrently adjusts and outputs the second sequence during the writing of the new physical master.

Brief Description of Drawings

FIG. 1 generally illustrates a storage medium formatted in accordance with various embodiments of the present invention, the storage medium exemplified without limitation as a DVD-9 optical disc.

FIG. 2 shows a functional block diagram for a reader system configured to read the storage medium of FIG. 1.

FIG. 3 sets forth a physical pattern of symbols placed onto the storage medium of FIG. 1, along with a corresponding readback pattern obtained therefrom using the reader of FIG. 2.

FIG. 4 is a functional representation of a multi-layer construction of the exemplary storage medium of FIG. 1.

FIG. 5 is a functional process representation of a mastering and replication facility used to generate a population of replicated storage media nominally identical to the storage medium of FIG. 1.

FIG. 6 depicts a writer system utilized during the processing of FIG. 5 to create a physical master.

FIG. 7 provides generalized representations of different types of media successively generated during the processing of FIG. 5.

FIG. 8 illustrates a particular methodology for forming a new physical master.

FIG. 9 illustrates another methodology for forming a new physical master.

FIG. 10 sets forth a system for forming a new physical master in accordance with various embodiments of the present invention that overcome limitations associated with the methodologies of FIGS. 8-9.

FIG. 11 shows representative transduced data sequences and associated digital samples obtained thereof by the system of FIG. 10. FIG. 12 sets forth a graphical representation of a histogram of symbol length distributions in the digital samples obtained by the system of FIG. 10.

FIG. 13 sets forth a corresponding graphical representation of adjusted symbol length distributions obtained by the operation of the system of FIG. 10. FIG. 14 shows a frequency domain representation of further digital samples obtained by the system of FIG. 10.

FIG. 15 is a flow chart for a REMASTERING PROCESS routine, generally illustrative of steps carried out in accordance with various embodiments of the present invention.

Detailed Discussion

FIG. 1 depicts an exemplary storage medium 100 formed in accordance with various embodiments of the present invention. While not limiting, the medium 100 is contemplated as a multi-layer optical disc formatted in accordance with the DVD- 9 standard to store user data, such as an audio-visual (AJV) work (e.g., a full-length movie with associated data). The medium 100 ("disc") is contemplated as having been formed during a mastering/replication process whereby a population of nominally identical discs are formed and packaged for authorized distribution through normal commercial channels. The disc 100 has a data storage area 101 in which data are stored along a number of concentric tracks that are preferably arranged along a continuous spiral. The tracks are accessed by a readback system 102 as shown in FIG. 2, contemplated as comprising a conventional DVD reader.

A motor 104 selectively rotates the medium 100 at a selected constant linear velocity (CLV) rate, in this case at some multiple of the specified DVD rate. A readback mechanism 106, characterized as an optical pickup, includes a linear actuator 108 which radially advances a light emitting transducer (head) 110 to follow the circumferentially extending tracks defined on the respective recording layers of the DVD. It is contemplated that the tracks in each layer are arranged as a continuous spiral from one radial extent of the medium 102 to the other, such as from the innermost diameter (ID) to the outermost diameter (OD), although such is not limiting to the practice of the various embodiments disclosed herein. A readback signal is transduced from the transducer 110 and provided to a readback processor block 112. The readback signal is preferably characterized as a frequency modulated (FM) pattern sequence with transitions at symbol boundaries (in this case, from 3T to 14T where T is the nominal channel frequency, or clock rate). The readback processor block 112 applies appropriate pattern detection, demodulation and error correction to recover the originally stored content from the medium 100.

The recovered data are thereafter sequentially provided to an associated I/O device 114. The content can take any number of forms, such as audio, video, computer programming, etc. The I/O device 114 can accordingly comprise an audio receiver, a video processor, a television display, a personal computer, etc.

The data are preferably stored on the medium 100 along the tracks as a physical pattern 116 of pits and lands, such as generally illustrated in FIG. 3. The pits are denoted as ovals which extend into an embedded pre-recorded layer of the disc at a selected depth. The physical pattern 116 constitutes a sequence with symbol lengths of 1OT, 5T, 4T, 8T, 1 IT, 6T and 7T, where T is the channel clock rate (such as T=26.16 MHz for IX DVD recording).

The processor 112 of FIG. 2 maintains the rotational rate of the medium 100 so as to achieve and maintain frequency lock on the readback data output by the transducer 110. The symbol lengths in the pattern 116 are selected by encoding the original data with a suitable modulation scheme, such as 8/16, to provide encoded data that observes certain run length limited (RLL) and other constraints. It will be appreciated that different formats often have different RLL constraints; for example, BD discs generally employ symbol lengths from 2T to 9T in length, etc. After suitable processing, a frequency modulated readback pattern 118 is obtained from the sequence 116. The readback pattern 118 has signal transitions that optimally correspond to the boundaries in the physical pattern between adjacent pits and lands. This readback pattern 118 is decoded by the processor 112 to provide the originally unencoded user data, which is then output to the output device 114.

As noted above, the exemplary medium 102 is contemplated as a DVD-9 with two embedded pre-recorded layers. These layers are generally illustrated in FIG. 4 as "layer 0" 120 and "layer 1" 122, respectively. It will be appreciated that other numbers and configurations of layers can alternatively be used as desired.

The first layer 120 (layer 0) has a lead-in area 124 followed by a program area 126 and a middle area 128. The second layer 122 (layer 1) has a middle area 130, a program area 132 and a lead-out area 134. As will be recognized, the respective sizes of the various areas shown in FIG. 2 in terms of data storage capacity are not represented to scale; rather, the data capacities of the program areas are very large as compared to the lead-in, lead-out and middle areas.

Content information for the disc 100 is stored in the lead-in area 124 in the form of a table of contents, TOC. The TOC identifies the collective contents of the program areas 126, 132 in a standardized manner in terms of title, length, elapsed times, number and locations of chapter divisions, etc.

During a sequential readback operation, the respective layers 120, 122 are read in the direction shown. The transducer 110 (FIG. 1) will locate the lead-in area 124, access the TOC and initiate recovery of the contents of the program area 126 on layer 0. At the end of the program area 126, the head 110 will adjust focal depth to the appropriate level to read layer 1, and continue with the recovery of the contents of the program area 132 until the lead-out area 134 is reached, signifying the end of the disc 100. The middle areas 128, 130 serve as buffer areas and are typically skipped.

The respective layers 120, 122 are preferably formed using an optical disc mastering and fabrication facility 140 as generally depicted in FIG. 5, which operates to generate a population of replicated discs (replicas) nominally identical to the exemplary disc 100. User content for the discs fabricated by the facility 140 is provided by a content source 142. The content source 102 can comprise a number of different types of facilities depending on the type of content. For example, if audio discs are to be formed the content source may comprise a recording studio; if video discs are to be formed the content source may comprise a movie production facility; if computer ROM discs are to be formed the content source may comprise a software development house, etc. The content source may represent a combination of these or other types of facilities, as required. The content source can provide the content to the facility 140 in a number of ways, such as electronically or through the transfer of a physical medium with the content thereon. The received content is subjected to an initial processing (authoring) step at block 144, which prepares the data such as in accordance with the so-called Disc Description Protocol, or DDP® standard, licensed by the assignee of the present application. The DDP® standard provides a structured methodology whereby the received data set can be encoded and provided with the requisite instruction set files to direct the formatting of the user data. As will be recognized, DDP® files are used to describe the content files for various types of disc formats, including CD, DVD, HD-DVD, BD, etc.

A mastering process takes place at block 146, whereby master discs are formed for each of the recording layers 120, 122. Preferably, an encoder/formatter modulates a laser beam recorder (LBR) to selectively expose a spun layer of photoresist on a base glass disc to provide a sequence of physical patterns therein. The glass master discs are subjected to appropriate processing at block 148 to form metalized stampers with pit and land sequences associated with the desired arrangement for each layer.

The stampers from block 148 form individual substrates with the associated recording layers thereon using an injection molding process or similar at block 150. After testing the layers at block 152, the layers are brought together to form completed discs at block 154. The completed discs are tested at block 156, and packaged and shipped at step 158. This processing provides a population of nominally identical replica discs 160. It is contemplated that the foregoing processing blocks are carried out in an automated manufacturing environment under the direction and control of a server 162. Associated information, history tracking and data accumulation with regard to the manufacturing process are stored in server memory 164.

FIG. 6 sets forth a functional block representation of a writer system 170 utilized during the aforementioned authoring and mastering blocks 144, 146. The input content data are provided from a storage location 172 to a signal processing block 174. The signal processing block 174 operates under the control of a top-level control processor block 176, which also controllably rotates a glass master 178 at a desired velocity via motor 180. The input data are processed by the signal processing block 174 and forwarded to a modulation (MOD) block 182, which applies an appropriate run length limiting (RLL) encoding to generate a frequency modulated (FM) output driver signal such as depicted at 1 18 in FIG. 3. For DVDs, the output of the encoder 182 may be an EFM+ signal with 8/16 encoding.

The modulation signal from the encoder operates to selectively modulate a light transducer 184, which selectively exposes a layer of photoresist or similar material on the glass master 178 in relation thereto as the transducer 184 is radially advanced across the medium via actuator 186. Without limitation, certain components shown in FIG. 5 preferably form a conventional laser beam recorder (LBR), including the control, motor, transducer and actuator blocks 176, 180, 184 and 186.

FIG. 7 provides a sequential depiction of the articles formed by the process of FIG. 5: a glass master 178; a resulting stamper 180 formed from metallization processing of the master 178, a recording layer 182 formed from the stamper, and a completed multi-layer disc 184 formed from the layer 182.

The stamper 180 is a mirror image of the master 178 and layer 182 so as to form the desired pit and land sequence during the layer formation process. The multi-layer disc 184 includes the layer 182 as well as a second layer 186 formed from a separate master and stamper (not shown). An intervening separation material 188 provides the desired separation distance between the respective layers 182, 186 in the completed disc 184.

Referring again to FIG. 5, it will be recalled that the disc fabrication process results in a population of replicas 160 which are offered through normal commercial channels. As in other business endeavors, the number of replicas 160 formed during the production run may be based on an estimated demand for such replicas. If additional authorized replicas are subsequently desired, another production run may need to be carried out by the facility 140 (or by a different facility under control of the content source). If the stampers generated during block 148 of FIG. 5 are still available, this additional production run may be carried out by reusing the stampers to repeat the processing of blocks 150 through 158. However, if the stampers are not available, then a remastering process may need to take place to generate a new master disc from which a set of stampers can be derived for the subsequent production run.

Prior approaches include recovering the content from an original data file (or a replicated disc from the initial production run), and applying new encoding processing to generate the FM modulation pattern. A problem with this approach is that the content may not be readily recoverable from the replicated disc. Moreover, embedded copy protection and/or disc authentication systems may not be properly transferred using this approach.

FIG. 8 shows one such remastering system 200. A previously generated replica disc 160 (FIG. 5) is read by a reader 102 (FIG. 1) to output the originally stored, unencoded user data to a computer 202, which stores the data in a suitable location, such as hard disc drive (HDD) 204. A meta-data generator 206 operates to generate the necessary meta-data, such as the aforementioned DDP® instruction sets. The content and meta-data are supplied to an encoder/formatter block 208 which operates to generate and output a frequency modulated (FM) signal to an LBR block 210. The LBR 210 generates a new physical master 212, which is utilized in a processing flow such as shown in FIG. 5 to provide a new production run of replicated discs. It will be appreciated that the processing of FIG. 8 requires the ability of the system 200 to access all of the relevant data and content on the replica disc 160 to facilitate proper operation of the resulting new master 212 and ultimately, the associated new run of replicated discs. Accordingly, both knowledge of and permission to utilize any and all copy protection and other access restriction systems on the original replica 160 must be granted. This is important to ensure that the replicated discs have the necessary features present on the discs to operate properly. It is also important so as to not run afoul of applicable laws in various jurisdictions, such as the Digital Millennium Copyright Act (DMCA) in U.S. Copyright Law. A problem arises when such knowledge and permission are restricted through the use of digital rights management (DRM) schemes such as the well- known Content Scramble System (CSS) encryption used on many types of DVDs. As will be recognized, access and decoding of CSS encoded sectors are highly controlled and restricted to authorized licensees, and accordingly prevents the removal of content encoded by such CSS encoding. Similarly, other DRM schemes provide certain types of features, such as specifically created errors in the error detection and correction (EDC) scheme, so unless special processing takes place to replicate these features in the replicated discs, the replicated discs may not function as intended.

A way to avoid these and other issues with the system of FIG. 8 is to simply provide a bit-for-bit readback stream from the replica disc 160, and supply these to the LBR 210 to create the new physical master 212. This alternative scheme is generally depicted in FIG. 9. The pick-up signals from the reader 102 may include the FM signal (such as 1 18 in FIG. 3), as well other tracking signals indicative of lower frequency groove or wobble signals present in the tracks themselves.

An advantage of the approach of FIG. 9 is that no decoding is necessary of the actual content; ideally, any features on the replica disc, either from a data standpoint or wobble signal standpoint, can be placed on the master as well. Thus, any DRM schemes employed on the replica disc relating to encryption, error induction, etc. are generally transferred bit-by-bit to the new glass master 212, and no decoding of these schemes is necessary.

A disadvantage, however, is that features may be placed onto the replica 160 that specifically prevent a lead-in to lead-out sequential reading of the disc, such as discussed in U.S. Patent No. 6,477, 124 to Carson, assigned to the assignee of the present application. Moreover, any signal degradations or other changes brought on by the reading of the replica copy, including misdetected symbol lengths, would be directly transferred to the new physical master 212. In such cases, the second run of replicas will not have the same characteristics as the first run, and will likely be degraded in quality and/or performance as compared to the first run.

Accordingly, FIG. 10 provides a system 220 that overcomes these and other limitations in the generation of a new physical master such as 212. As before, a selected replica 160 is read by a reader 102 to output a sequence of pick up signals. At this point it will be noted that while a selected replica 160 is shown in FIG. 10, it will be appreciated that such is not limiting; more generally, any physical medium such as the master 178, stamper 180, layer 182 or disc 184 of FIG. 7, or archived signals obtained therefrom, can be utilized as desired. It is contemplated that any number of pick-up signals may be obtained depending on the format of the replica 160; for purposes of the present discussion, a first pick-up signal is passed along path 222 to provide the FM signal representing the sequence of symbols on the disc 160, and a second pick-up signal is passed along path 224 to provide the wobble signal indicative of wobble information supplied along the tracks.

Each of these pick-up signals is sampled by an associated sampling (digitizing) circuit 226, 228. The sampling circuits 226, 228 are clocked by a digitization clock 230. While any suitable sampling rate can be used, in a preferred embodiment the sampling takes place at a rate that is higher than the normal clock rate of the respective samples, such as on the order of about 1OX or higher. The sampling clock can be derived from the frequencies of the input signals, or may be generated independently of the input signals. It is generally preferred, however, that each of the sampling rates be derived from a common source to maintain time synchronization therebetween.

With regard to the particular sampling rates, a IX DVD FM data modulation signal with a channel clock rate of nominally T=26.16 MHz may be sampled at 10X, or about 261.6 MHz. A conventional wobble signal may have a primary frequency component of about 22.05 KHz, so the sampling of the wobble signal may take place at 10X, or about 220.5 KHz. It is not necessary that the sampling be an integer of the frequencies of the base sampled signals (e.g., a value such as 3.5X, etc. may be used), nor is it necessary that the sampling be higher than the frequencies of the base sampled signals (e.g., a less-than unity value such as 0.65X may be used). By way of illustration, FIG. 1 1 shows an exemplary FM data modulation signal 232 sampled at a selected rate to provide a first sequence of digital samples 234, and an exemplary wobble signal 236 sampled at a selected rate to provide a second sequence of digital samples 238. The samples can be taken at the same frequency for both signals, or different sampling frequencies can be used as shown in FIG. 11. As noted above, oversampling is preferred but not necessarily required. For purposes of clarity, the data modulation signal 232 depicted in FIG. 1 1 is the result of the readback of the medium by the reader 102 to detect the physical pattern of symbols (pits and lands) stored thereon. Ideally, this modulation readback signal will nominally match the initial modulation signal supplied during the initial mastering process by the modulation circuit 182 (FIG. 5) to modulate the write transducer 184 and write the initial physical pattern to the glass master 178.

Similarly, the wobble signal 236 of FIG. 11 is the result of the readback of the medium by the reader 102 to detect radial variations along the tracks for servo control and other purposes, such as copy protection and authentication. Ideally, this wobble readback signal will nominally match the initial wobble signal supplied during the initial mastering process by the control circuit 176 (FIG. 5) to actuator carriage 186, thereby placing such wobble pattern onto the glass master. Real world effects however, including variations in the medium as a result of the manufacturing process and offsets associated with the writer and reader circuitry, will tend to induce signal degradations in these readback signals over what was originally intended to be stored to the medium.

Continuing with FIG. 10, the digital samples obtained by the sampling circuits 226, 228 are forwarded to a signal analysis and adjustment circuit 240. The adjustment circuit 240 temporarily stores the sample sequences as a series of digitized files in a storage location 242, such as an HDD. Other suitable locations may be DRAM memory, flash, etc. It will be appreciated that the storage location 242 operates to temporarily buffer the samples, although longer term retention can also be achieved as desired. The adjustment circuit 240 analyzes the sample sequences for signal degradation effects such as signal asymmetry, short or long run lengths, undesired frequency components, etc. Such degradations are corrected in the digitized files in the storage 242 to provide nominally pristine sequences that meet the associated specifications for the disc. Various levels of analysis complexity can be applied, depending on the requirements of a given application. The adjustment circuit 240 preferably comprises a high speed programmable processor with suitable detection and correction algorithms supplied in associated programming, although other configurations including a hardware based solution can be utilized as desired.

In some embodiments, the detection and correction algorithms utilized by the adjustment circuitry examine the run lengths of the respective symbols set forth in the digitized sequences, and correct the symbol lengths to precise run length values. In this way, deviations in symbol lengths are corrected. For example, a particular symbol in the digitized sequence with a detected length of about 4.8T may be adjusted so as to reflect an adjusted length of 5T. As desired, greater knowledge with regard to legal bit sequences, such as the encoding tables used to generate the symbol sequences and the specific maximum and minimum symbol lengths can be used to aid in the appropriate selection of adjusted symbol values. In other embodiments, more advanced detection and correction algorithms are utilized that have a prior knowledge of the specified format for the data stored on the replica 160, such as the particular EDC/ECC system utilized to generate the respective encoded data. In such cases, at least some levels of symbol length error detection and correction can be utilized by checking both the initially digitized symbol sequence and the proposed corrected symbol sequence against the specific rules called out for the disc format. Without limitation, these rules can include the aforementioned EDC/ECC scheme as well as digital sum variation (DSV), modulation scheme, encryption system, etc.

Irrespective of the particular signal analysis and adjustment algorithms employed, the resulting operation of the adjustment circuit 240 streams the output adjusted sequences to a signal reconstruction block 244. Where multiple streams of sequences are evaluated and adjusted, the circuit 240 operates to maintain time synchronicity therebetween in the output adjusted streams.

The reconstruction block 244 generates new modulation signal(s) clocked by one or more reconstruction clock(s) supplied by a reconstruction clock generator 246. The output signals are supplied to an associated LBR 210 to generate the new physical master 212.

To further illustrate preferred operation of the circuitry 220 of FIG. 10, FIG. 12 shows a generalized representation of an exemplary histogram 248 of symbol length values in the modulated data sequence from the replica 160. Symbol length distributions for 3T to 7T are shown, although it will be appreciated that for the exemplary DVD-9 replica 160, additional values would be obtained for symbol lengths of 8T to 14T. These latter distributions have been omitted for clarity.

As shown in FIG. 12, the digitized sequences provide generally Gaussian (bell-curve) distributions for each symbol lengths, with maximum values in the vicinities of the desired pristine values but with tails that overlap. This means that a substantial number of symbols from the detected sequence have values that are of intermediate length; for example, the non-zero count between the 3T and 4T distributions indicates that at least some number of detected samples in the digitized sequence reflect lengths in the vicinity of about 3.5T. One problem with this, of course, is determining whether a given sample of about 3.5T was intended to be a 3T symbol or a 4T symbol (or even some other symbol length). However, as a result of the application of the aforementioned detection and adjustment algorithms, accurate estimates of the intended values can be made and the digitized files can be adjusted to supply samples with nominally pristine values, such as generally depicted at 250 in FIG. 13. While the distributions in FIG. 13 are rectangular, it will be appreciated this is merely to represent the enhanced distributions and associated separation distances that can be achieved. Thus, the adjusted symbol distributions can take on a bell-shaped curve as before, or each respective symbol can be adjusted to an exact value so that the distributions substantially resemble vertically extending straight lines.

At this point it will be noted that the level of precision in the adjustment carried out by the adjustment circuit 240 can further be tailored by other factors. For example, it may be desirable to individually adjust particular pit/land transitions away from the pristine values depicted in FIG. 13 in a downstream processing block. This may be carried out to further enhance manufacturability or to embed hidden data onto the replicated disc, such as taught by U.S. Patent No. 6,469,969 to Carson et al., assigned to the assignee of the present application. Such embedded processing may further be detected initially in the analysis of the detected samples and replaced in the adjusted sequence supplied to the reconstruction block 244.

FIG. 14 similarly shows a frequency domain representation 252 of the wobble signal samples obtained by the circuitry 220 of FIG. 10. The distribution of frequency components shown in FIG. 14 generally serves to identify different main components in the wobble signal. For example, when a primary frequency of about 22.05 KHz is utilized, this may be generally reflected by a localized increase (spike) 254 in the frequency domain representation 252.

The presence of additional frequency components, such as represented by localized increase 256, can also be readily ascertained. Such additional frequency components may be spurious and therefore eliminated in the adjusted samples, or may be retained or even enhanced as such frequency components may relate to copy protection or other authentication features of the replica 160. It will be appreciated that the system 220 has particular utility for certain types of media such as audio CDs and A/V BD discs which generally provide a continuously extending spiral from lead-in to lead-out. In such cases, an unbroken sequence of digitized samples can be obtained without the need to account for disruption zones or other features on the medium that reduce the ability to obtain a continuous bit-for-bit readout of the medium contents. However, even the presence of various disruption zones can be readily accommodated.

Upon the detection of each such disruption, a notation of the location of the disruption can be made, the data collection sequence can be temporarily halted, and the system can carry out a seek to find the extent and configuration of the disruption feature including, as desired, the sampling of any data therein. The continued sampling on the other side of the disruption can thereafter be resumed. In this way, even such discontinuities can be accurately reproduced on the new physical master. It will be noted at this point that, generally, higher sampling rates allow a more accurate determination to be made with regard to the actual symbol lengths and other characteristics of the replica 160. For example, it can be seen that if the sampling takes place at the same rate as the channel clock rate (or at a lower rate), the decisions with regard to whether a particular input symbol is a given length will be initially made by the sampling circuitry 226, 228. For example, a symbol of length 3.5T will be initially digitized as a 3T or a 4 T in the initially stored digitized files. This is not necessarily a drawback, particularly in the case wherein additional rules are applied to determine whether the symbol was intended to be a 3 T or 4T symbol (or even a 7T symbol with an inadvertent transition therein).

Another advantage of the circuitry 220 is that the signal analysis and adjustment operation of block 240 can be carried out off-line, allowing the reconstruction and mastering to take place at a later time while the reconstructed samples are retained in the memory 242. In preferred embodiments, however, the circuitry 220 operates to stream the data (after adjustment and reconstruction) directly from the replica 160 to the new master 212. A further advantage of this latter approach is that different frequencies can be utilized between the upstream sampling and the downstream clocking. For example, the sampling of the initial signals may take place at 1OX while the signal reconstruction and driving of the LBR can be performed at perhaps 5X, with the temporary storage 242 operating as a data buffer. Similarly, the upstream sampling can take place at a lower rate (or the same rate) at which the downstream clocking takes place.

FIG. 15 provides a generalized flow chart for a REMASTERING PROCESS routine 300, illustrative of various steps carried out by preferred embodiments as discussed above. Generally, at step 302 a transduced frequency modulated (FM) pattern sequence is obtained by reading an initial medium. In the present example this is contemplated as occurring by the reader system 102 of FIG. 10 using an associated transducer (see FIG. 1) to read the replica 160. The transduced sequence will generally comprise a sequence of 3T to 14T length symbols where T has a base value of 26.16 MHz (at IX reading rate).

The transduced sequence is next sampled at step 304 using digital sampling, preferably at a frequency substantially higher than the channel clock rate. As noted above, this frequency may be 1OX or more of the channel clock rate. Preferably, this sampling frequency is used to obtain relatively high quality digital representations of the analog pattern sequence, and to discern the precise locations of various transitions in order to differentiate the actual symbol stream in the initially received sequence. The digital samples are preferably stored in a memory location, such as the temporary storage 242 in FIG. 10. The samples are preferably streamed from the replica 160 and sampled without regard to differentiating between content and overhead (error correction, subcode, etc.) types of data.

Processing of the digital samples next takes place at step 306. As noted above, such processing preferably includes adjustments of individual timing of transitions to conform to the existing system parameters. For example, the 3T-14T timing edges are well specified by existing DVD standards, and so the samples are adjusted to meet these standards.

Other processing can preferably take place during this step as well. For example, without specifically examining the content, knowledge of the error correction schemes, synchronization patterns, modulation schemes, run length limiting rules, etc. can be readily used to detect and correct misidentified symbols in the sequence. For example, a portion of the digitized pattern that provides a 6T followed by a 4T symbol might be found to have actually been intended to be some other sequence (e.g., a 7T, 3T sequence) based on the above information. Hence, errors in the digitized sequence can be detected without reading the actual content of the sequence.

Once the digital samples have been adjusted, a new FM pattern sequence is generated therefrom at step 308. This new pattern will be substantially "pristine" in that it fully conforms to existing patterns and meets all system parameters for the associated medium type. The new pattern is thereafter used to generate a new physical master at step 310. This latter step can include, as desired, individual adjustments of pit and land transitions, signal levels, etc. appropriate for the associated manufacturing process as before. In this way, a new batch of replicas generated from the new master will nominally have the exact same readback characteristics as the replica 160 from the initial production run.

The foregoing embodiments present important distinctions and advantages over the art. While it may be well known to evaluate a readback signal from a first disc to generate a new, compensated modulation to write a new disc, such processing in the prior art generally merely operates to tweak the existing process in an iterative effort to obtain readback quality at a desired level for a given production run. By contrast, the methodology set forth herein enables a new production run to have a verified baseline pattern sequence for a new master. Of course, such iterative processes in the prior art can be additionally performed after the above methodology is implemented, as desired, to ensure the subsequent production run provides output signals with desired characteristics.

Claims

CLAIMS:

1. A method comprising steps of: sampling a transduced pattern sequence at a selected sampling frequency to provide a sequence of digitized samples; selectively adjusting the sequence of digitized samples to provide a sequence of adjusted digitized samples with signal transitions corresponding to preselected symbol lengths; and writing the sequence of adjusted digitized samples to a medium to form a new physical master from which a population of replicated media can be formed.

2. The method of claim 1 , further comprising using the new physical master to form a stamper, using the stamper to form a population of replicated recording layers, and applying a bonding process to the replicated recording layers to form said population of replicated media.

3. The method of claim 1, further comprising a prior step of transducing the transduced pattern sequence from a physical medium associated with an initial production run of replicated media, and using the new physical master to form said population of replicated media in a subsequent production run.

4. The method of claim 1, wherein the transduced pattern sequence comprises a first transduced pattern sequence comprising a frequency modulated data signal from an optical medium, and wherein the method further comprises concurrently transducing a second transduced pattern sequence comprising a wobble signal from the optical medium to provide a second sequence of digitized samples, selectively adjusting the second sequence of digitized samples, and concurrently outputting the adjusted second sequence of digitized samples during the writing step to form the new physical master.

5. The method of claim 1, wherein the transduced pattern sequence has signal transitions at a channel clock frequency, and wherein the selected sampling frequency of the sampling step is greater than the channel clock frequency.

6. The method of claim 1, wherein the selectively adjusting step comprises identifying initial symbol lengths of symbols expressed in the sequence of digital samples and adjusting said symbol lengths to preselected symbol lengths without decoding content represented by said initial symbol lengths.

7. The method of claim 6, wherein the selectively adjusting step further comprises applying at least a selected one of a predetermined run length limited (RLL) rule or a error detection and correction (EDC) rule to form the adjusted digitized samples

8. The method of claim 1, wherein the preselected symbol lengths comprise lengths of from 3T to 14T, wherein T is a channel clock rate, and wherein the adjusted digitized samples are adjusted to nominally have transitions of from 3T to 14T.

9. An apparatus comprising: a sampling circuit which samples an input transduced pattern sequence at a selected sampling frequency to provide a sequence of digitized samples; an adjustment circuit coupled to the sampling circuit which selectively adjusts the sequence of digitized samples to provide a sequence of adjusted digitized samples with signal transitions corresponding to preselected symbol lengths; and a reconstruction circuit coupled to the adjustment circuit which directs the writing of the adjusted digitized samples to a medium to form a new physical master from which a population of replicated media can be formed.

10. The apparatus of claim 9, further comprising a writer system coupled to the reconstruction circuit which modulates a write transducer responsive to a modulation signal generated by the reconstruction circuit in relation to the adjusted digitized samples to write the new physical master.

11. The apparatus of claim 10, further comprising a stamper formed from the new physical master configured to form a population of recording layers via a molding process.

12. A replicated medium formed by the apparatus of claim 9.

13. The apparatus of claim 9, further comprising a reader which transduces the transduced pattern sequence from a physical medium associated with an initial production run of replicated media, wherein the new physical master is configured to form said population of replicated media in a subsequent production run.

14. The apparatus of claim 9, wherein the transduced pattern sequence comprises a first transduced pattern sequence comprising a frequency modulated data signal from an optical medium, and wherein the apparatus further comprises a second sampling circuit which concurrently samples a second transduced pattern sequence comprising a wobble signal from the optical medium to provide a second sequence of digitized samples, wherein the adjustment circuit further operates to selectively adjust the second sequence of digitized samples, and wherein the reconstruction circuit concurrently outputs the adjusted second sequence of digitized samples to form the new physical master.

15. The apparatus of claim 9, wherein the transduced pattern sequence has signal transitions at a channel clock frequency, and wherein the selected sampling frequency of the sampling step is greater than the channel clock frequency.

16. The apparatus of claim 15, wherein the selected sampling frequency is greater than or equal to about 1OX the channel clock frequency.

17. The apparatus of claim 9, wherein the adjustment circuit operates to identify initial symbol lengths of symbols expressed in the sequence of digital samples and to adjust said symbol lengths to preselected symbol lengths without decoding content represented by said initial symbol lengths.

18. The apparatus of claim 9, further comprising a memory storage location coupled to the adjustment circuit which temporarily stores the sequence of digitized samples and the sequence of adjusted digital samples.

19. The apparatus of claim 9, wherein the preselected symbol lengths comprise lengths of from 2T to 9T, wherein T is a channel clock rate, and wherein the adjusted digitized samples are adjusted to nominally have transitions of from 2T to 9T.

20. An apparatus comprising: a reader system which reads a storage medium to produce a transduced pattern sequence at a selected sampling frequency; and first means for sampling the transduced pattern sequence to provide a sequence of digitized samples, for selectively adjusting the sequence of digitized samples to provide a sequence of adjusted digitized samples with signal transitions corresponding to preselected symbol lengths, and for writing the sequence of adjusted digitized samples to a medium to form a new physical master from which a population of replicated media can be formed, said replicated media nominally identical to said storage medium.